ML14309A190

Attachment 2, Calculation 1401289.301, Revision 0, ANO Leaking Flaw Evaluation.

ML14309A190
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Site:	Arkansas Nuclear
Issue date:	10/31/2014
From:	Roukema A Structural Integrity Associates
To:	Office of Nuclear Reactor Regulation
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2CAN101403 1401289.301, Rev. 0
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ATTACHMENT 2 TO 2CAN101403 STRUCTURAL INTEGRITY ASSOCIATES CALCULATION 1401289.301

StructuralIntegrity Associates, Inc! File No.: 1401289.301 Project No.: 1401289 CALCULATION PACKAGE Quality Program: Z Nuclear L] Commercial PROJECT NAME:

ANO Leaking Flaw Evaluation CONTRACT NO.:

10423246, Change Request No. 00109841 CLIENT: PLANT:

Entergy Arkansas, Inc. Arkansas Nuclear One, Unit 2 CALCULATION TITLE:

Evaluation of a Through-Wall Leak in a Service Water Tee (Dwg 2HCC-2003-1)

Document Affected Project Manager Preparer(s) &

Revision Pages Revision Description Approval Checker(s)

Signature & Date Signatures & Date 01 - 12 Initial Issue Preparer:

Eric J. Houston Adam C. Roukema 10/31/2014 10/31/2014 Checker:

Brad P. Dawson 10/31/2014 Page 1 of 12 F0306-01 R I

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Table of Contents

1.0 INTRODUCTION

..................................................................................................... 3 2.0 TECHNICAL APPROACH ...................................................................................... 3 3.0 DESIGN INPUTS AND ASSUMPTIONS .............................................................. 3 4.0 CALCULATIONS ..................................................................................................... 4 4.1 Minimum Required Wall Thickness ............................................................ 5 4.2 Applied Loads .............................................................................................. 5 4.2.1 Hoop Stress ................................................................................................... 5 4.2.2 A xial Stresses..................................................................................................... 5 4.3 Stress Intensity Factor Calculations .............................................................. 6 4.4 Critical Fracture Toughness Determination .................................................. 7 5.0 RESULTS ............................................................................................................. 8

6.0 CONCLUSION

S ...................................................................................................... 8

7.0 REFERENCES

......................................................................................................... 9 List of Tables Table 1: Applied Moment Loading for Bounding Moments ............................................. 10 Table 2: Jic Values for A106 Gr. B Carbon Steel from NRC's Pipe Fracture Database [9].. 11 Table 3: Axial and Circumferential Structural Factors [2] ............................................... 12 Table 4: Load Combinations for Circumferential Flaw Analyses ...................................... 12 Table 5: Pressure Blowout Check ....................................................................................... 12 File No.: 1401289.301 Page 2 of 12 Revision: 0 F0306-01 RI

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1.0 INTRODUCTION

Arkansas Nuclear One has identified a pinhole leak in a 6-inch branch connection (Sweep-o-let) in the service water system. The system is safety related, and therefore requires an evaluation to demonstrate operability. The objective of this calculation is to determine the allowable through-wall flaw lengths in accordance with ASME Code Case N-513-4 [1].

2.0 TECHNICAL APPROACH The flaw evaluation herein is based on the criteria prescribed in ASME Code Case N-513-4, allowing for the temporary acceptance of through-wall flaws in moderate energy Class 2 or Class 3 piping. N-513-4 allows non-planar, through-wall flaws to be characterized and evaluated as planar (i.e., crack-like), through-wall flaws in the axial and circumferential directions.

In addition to straight pipe, N-513-4 evaluation criteria includes rules for the evaluation of piping components such as elbows, branch tees and reducers. Flaws in these components may be evaluated as if in straight pipe provided the stresses used in the evaluation are adjusted to account for geometric differences.

Details are provided in N-513-4 for determining these adjusted stresses. The leaking flaw is in the carbon steel sweep-o-let, near the dissimilar metal weld at the adjoining stainless steel elbow. Therefore, the evaluation approach for branch connections in N-513-4 is appropriate. Although the attached elbow material has significantly higher toughness than the carbon steel (which if used would result in a much larger allowable through-wall flaw) the influence of the higher toughness on the allowable through-wall flaw is ignored and the system is evaluated as only carbon steel.

N-513-4 has been approved and published by ASME. It is recognized in ASME committee that the technical approach is very conservative. Simple treatment of piping component flaw evaluation using hand calculations was an important objective in the development of the approach recognizing the trade-off being conservative results. N-513-4 allows for alternative methods to calculate the stresses used in the analysis to reduce conservatism. N-513-4 has not been generically reviewed by the NRC.

Code Case N-513-4 evaluation criteria rely on the methods given in ASME Section XI, Appendix C [2].

Linear Elastic Fracture Mechanics (LEFM) criteria are conservatively employed as described in Article C-7000. Equations for through-wall stress intensity factor parameters Fm, Fb and F are given in the Code Case, Appendix I. Allowable flaw lengths are determined through iteration comparing calculated stress intensity factors to a critical fracture toughness defined in C-7200 of Section XI, Appendix C.

3.0 DESIGN INPUTS AND ASSUMPTIONS The piping design Code of Construction is ASME Section III - 1971 with Addenda through Summer 1971

[3] except for the items listed below:

A) Use ASME Section III - 1971 Winter 1972 Addenda, NC-361 1.1(b)(4)(c) and NC-3650 with Code Case 1606-1, for the following:

a. Moments b. Design Loading Combinations File No.: 1401289.301 Page 3 of 12 Revision: 0 F0306-O1 RI

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c. Section Modulus d. Stress Limits B) Use ASME Section III- 1974 [4], NC-3673.2 for the following:

a. Flexibility Factors b. Stress Intensification Factors The sweep-o-let material is ASME A105 Gr II carbon steel and the run piping is A106 Gr. B [5] carbon steel. For the analysis, A106 Gr. B carbon properties are conservatively used. In addition, the fracture toughness of the two materials are assumed to be comparable.

The following design inputs are used in this calculation:

1. Outside diameter = 6.625 inches [5, Line Item 14]

2. Nominal wall thickness = 0.280 inch (based on standard pipe size) [5, Line Item 14]

3. Design temperature = 130 0 F [6, Page 114]

4. Design pressure = 150 psig [6, Page 114]

5. Material stress allowable = 15 ksi [7, PDF Page 19]

6. Young's modulus = 27,900 ksi [7, PD" Page 19]

7. NDE inspection results [8]

The moment loadings applied to the piping are obtained from the piping stress report [7] for the element located between nodes 25 and 225. The bounding moments are shown in Table 1.

Determination of the fracture toughness, Jic, used in the evaluation is based on Section XI, Appendix C, C-8320 [2], which specifies that 'reasonable lower bound fracture toughness data' may be used to determine the allowable stress intensity factor, Kic. The NRC's Pipe Fracture Encyclopedia [9] contains numerous CVN test results for A106 Gr. B carbon steel at low temperature, which are reproduced in Table 2. The minimum reported value of 293 in-lb/in 2 is used in the analysis.

The following assumptions are used in this calculation:

1. Poisson's ratio is assumed to be 0.3.

2. The impact of weld residual stress on the structural stability of the observed flaw is assumed negligible. Weld residual stresses are secondary (i.e., self-limiting) and do not contribute significantly to gross structural failure in ductile materials in the presence of a through-wall flaw. In addition, the contribution, if any, to flaw growth due to secondary weld residual stresses is not required as the Code Case specifies a frequent re-inspection interval.

3. A corrosion allowance is not considered (the ongoing inspection requirements in Code Case N-513-4 address the possibility of flaw growth during the temporary acceptance period).

4.0 CALCULATIONS The applied stresses and resulting stress intensity factors are conservatively calculated using an evaluated wall thickness, teva, 0.175 inches.

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4.1 Minimum Required Wall Thickness An evaluation of ASME Section III, NC-3650 equations 3, 8, 9B, 9D, and 10 has been conducted using inputs discussed in Section 3.0. Based on these equations the minimum required wall thickness is 0.115 inch.

4.2 Applied Loads Axial and circumferential (i.e., hoop) stresses are calculated from the moment loads in Table I and the design pressure. The evaluated wall thickness, teval, is used to determine the section properties. The nominal wall thickness, tnom, is used to calculate the flexibility characteristic 'h' in accordance with the guidance of N-513-4.

4.2.1 Hoop Stress For the allowable axial flaw length on a branch tee, the hoop stress, ch, may be determined from Equation 13 ofN-513-4:

2-T Ufh = PD° (1) 2t where:

p = internal design pressure, psig D. = outside diameter, in t = evaluated wall thickness = teval, in 4.2.2 Axial Stresses For the allowable circumferential flaw length, the axial stress due to pressure, deadweight and seismic loading is presented below. For axial membrane stress due to pressure, am, Equation 14 of N-513-4 is used.

Note that there is a typo in the published version of this equation; the correct form is:

am = B,ip (2) 2t Bi is the primary stress index for pressure loading. As allowed by the Code Case, the primary stress indices B i and B 2 are taken from a more recent edition of the ASME Code [10, Table NB-3681(a)-I]. For branch connections, B1 is 0.5.

For axial bending stress, Gb, due to deadweight and seismic moments, Equation 15 of N-513-4 may be used:

orb = B2 D-Mb (3) 21 File No.: 1401289.301 Page 5 of 12 Revision: 0 F0306-01 R1

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where:

Mb = resultant primary bending moment, in-lbs. 4 I = moment of inertia based on evaluated wall thickness, in The coefficient B2 for branch connections is 0.5*C 2 (but not < 1.0) and [10, NB-3683.8]:

C2=.5 2/3 (=,r,)1/2 (1b5 (rm) (4) where:

Rm = mean nominal radius of run pipe, in Tr = nominal wall thickness of run pipe, in r'm = mean nominal radius of branch pipe, in T'b = nominal wall of branch pipe, in rp = outside nominal radius of branch pipe, in For axial bending stress, ce, due to thermal expansion, Equation 16 of N-513-4 may be used:

i DM(5) where:

i = stress intensification factor Me = resultant thermal expansion moment, in-lbs.

The stress intensification factor is calculated based on a welding tee as [4, Figure NC-3673.2(b)-l]:

0.9 h2/3 a r (6,7) where:

h = flexibility characteristic tn = nominal wall thickness of run piping, in r = mean radius of run piping, in 4.3 Stress Intensity Factor Calculations For LEFM analysis, the stress intensity factor, KI, for an axial flaw is taken from Article C-7000 [2] as prescribed by N-513-4 and is given below:

K, Kh +Kir where:

Kim = (SFm)Fc'h(lraIQ) 0 5 SFm = structural factor for membrane stress (see Table 3)

F = through-wall stress intensity factor parameter for an axial flaw under hoop stress (given in Appendix I of N-513-4)

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Gh = hoop stress, ksi a = flaw depth (taken as half flaw length for through-wall flaw per Appendix I of N-513-4), in Q = flaw shape parameter (unity per Appendix I of N-513-4)

Kir = Ki from residual stresses at flaw location (assumed negligible)

Only the hoop stress influences the allowable axial flaw length, which is a function of pressure.

For LEFM analysis, the stress intensity factor, K1, for a circumferential flaw is taken from Article C-7000

[2] as prescribed by N-513-4 and is given below:

K 1 =Kim +glb +Kir where: 05 Kim = (SFm)Fmam(7ra)

Fm = through-wall stress intensity factor parameter for a circumferential flaw under membrane stress (given in Appendix I of N-513-4) um = membrane stress, ksi Kr= [(SFb)Gb + ae]Fb(la)° 5 SFb = structural factor for bending stress (see Table 3)

Gb = bending stress, ksi ce = thermal stress, ksi Fb = through-wall stress intensity factor parameter for a circumferential flaw under bending stress (given in Appendix I of N-513-4)

Krr = Ki from residual stresses at flaw location (assumed negligible)

Note that the through-wall flaw stress intensity factor parameters are a function of flaw length.

Table 4 shows the specific load combinations considered herein for the allowable circumferential flaw calculations.

4.4 Critical Fracture Toughness Determination For LEFM analysis, the static fracture toughness for crack initiation under plane strain conditions, Kic, is taken from Article C-7000 [2] as prescribed by N-513-4 and is given below:

K-c J-CE 1000 where: 2 Jic = material toughness, in-lb/in E' = E/( 1-v2)

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Based on the design input listed above, KIc = 94.7 ksi-in° 5 . The allowable flaw lengths are determined iteratively by increasing flaw length until the stress intensity factor is equal to the static fracture toughness.

5.0 RESULTS Based on inputs in Section 3.0, moments in Table I and using equations from Section 4.0, the allowable through-wall flaw in the circumferential direction is 2.7 inches and the allowable through-wall flaw in the axial direction is 5.8 inches. The allowable through-wall flaw lengths are based on an evaluated wall thickness of 0.175 inch. Based on the inspection data given in Reference [8], the analyzed thickness and flaw lengths easily bound the observed thinning. Thus, the acceptance criteria of Code Case N-513-4 are met.

Code Case N-513-4, Paragraph 3.2(c) requires that the remaining ligament average thickness over the degraded area be sufficient to resist pressure blowout [1, Equation 8]. Table 5 shows the required average thickness, tc.avg, as a function of the equivalent diameter of the circular region, dadj, for which the wall thickness is less than tadj. Based on the inspection data given in Reference [8], the values in Table 5 easily bound the observed thinning. Thus, the Code Case requirement is met.

6.0 CONCLUSION

S Arkansas Nuclear One has identified a pinhole leak in a 6-inch branch connection (Sweep-o-let) in the service water system. Allowable through-wall flaw lengths have been calculated in accordance with ASME Code Case N-513-4. Because N-513-4 has not been generically reviewed by the NRC, justification for continued operation without repair or replacement until the next scheduled outage requires NRC review and approval.

The allowable through-wall flaw in the circumferential and axial directions is 2.7 inches and 5.8 inches, respectively. The allowable through-wall flaw lengths are based on an evaluated wall thickness of 0.175 inch. Table 5 shows the requirements to meet the Code Case pressure blowout limits.

The observed pinhole leak is easily bounded by the results of the analysis; thus, the acceptance criteria of Code Case N-513-4 are met. The system should be considered operable but degraded.

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7.0 REFERENCES

1. ASME Code Case N-513-4, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping Section XI, Division 1," Cases of ASME Boiler and Pressure Vessel Code, May 7, 2014.

2. ASME Boiler and Pressure Vessel Code,Section XI, Appendix C, 2001 Edition with 2003 Addenda.

3. ASME Boiler and Pressure Vessel Code,Section III, 1971 Edition with Addenda through Summer 1971.

4. ASME Boiler and Pressure Vessel Code,Section III, 1974 Edition.

5. Entergy Drawing No. 2HBC-33-2, Sheet 1, Revision 16, "Large Pipe Isometric Service Water Supply Header #1," SI File No. 1401289.201.

6. Entergy Calculation No. 88-E-0200-15, Revision 3, "P-T Calculation for Unit 2 Service Water System," SI File No. 1401289.201.

7. Entergy Calculation No. 90-D-2003-08, Revision 3, "Supply Piping Analysis for Piping in DCP 90-2003," SI File No 1401289.201.

8. Entergy UT Thickness Examination Report No. 2-BOP-UT-14-040, SI File No. 1401289.201.

9. Pipe Fracture Encyclopedia, US Nuclear Regulatory Commission, Volume 1, 1997.

10. ASME Boiler and Pressure Vessel Code,Section III, 2004 Edition.

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Table 1: Applied Moment Loading for Bounding Moments Notes:

I. Square Root Sum of the Squares (SRSS) is used to calculate moments from Reference [7].

2. Moments are from the bounding location, which is at node 225.

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Table 2: Jic Values for A106 Gr. B Carbon Steel from NRC's Pipe Fracture Database [9]

Database Reference Temperature (°C) Temperature (°F) JIC (kJ/m') JIC (Ibrin/inW) KIC(ksi-n) 2 24 75 97 552 133 2 24 75 336 1919 249 16 25 77 81 464 122 16 25 77 418 2386 277 16 25 77 270 1542 223 16 25 77 193 1104 189 22 24 75 224 1278 203 22 20 68 112 641 144 22 20 68 117 668 147 22 23 73 214 1223 199 22 20 68 167 954 175 22 20 68 223 1271 202 22 20 68 108 617 141 23 52 126 116 663 146 23 23 73 103 590 138 23 23 73 105 600 139 23 23 73 93 528 131 24 23 73 76 431 118 24 23 73 8g 469 123 24 57 135 51 293 _ 971_

25 23 73 77 439 119 25 23 73 70 400 114 25 57 135 62 356 107 90 20 68 235 1342 208 90 20 68 219 1251 201 90 20 68 255 1456 217 90 20 68 281 1605 228 90 20 68 281 1605 228 90 20 68 335 1913 248 90 20 68 421 2404 279 90 20 68 385 2198 266 90 20 68 175 999 180 90 20 68 172 982 178 90 20 68 178 1016 181 90 20 68 214 1222 199 90 20 68 275 1570 225 90 20 68 133 759 157 90 20 68 140 799 161 90 20 68 174 994 179 90 20 68 111 634 143 90 20 68 190 1085 187 90 20 68 71 405 114 90 20 68 110 628 142 90 20 68 104 594 138 90 20 68 104 594 138 90 20 68 97 5594 134 90 20 68 89 508 128 90 20 68 88 502 127 90 20 681 267 1525 222 File No.: 1401289.301 Page 11 of 12 Revision: 0 F0306-OIRI

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Table 3: Axial and Circumferential Structural Factors [2]

Service Level Membrane Stress, SFm Bending Stress, SFb A 2.7 2.3 B 2.4 2.0 C 1.8 1.6 D 1.3 1.4 Table 4: Load Combinations for Circumferential Flaw Analyses Load Combination Service Level P+DW+TH A P+DW+TH+OBE B P+DW+TH+DBE D Table 5: Pressure Blowout Check dadj tc,avg 0.25 0.01 0.75 0.03 1.25 0.04 1.75 0.06 2.25 0.08 2.75 0.10 3.25 0.11 3.75 0.13 4.25 0.15 4.75 0.17 5.25 0.19 File No.: 1401289.301 Page 12 of 12 Revision: 0 F0306-01 RI

ATTACHMENT 3 TO 2CAN101403 UT THICKNESS EXAMINATION REPORT 2-BOP-UT-14-040

• Entergy UT Thickness Examination Site/Unit: ANO-2 / 2 Procedure: CEP-NDE-0505 Outage No.: N/A Summary No.: FW-1 2HCC-2003-1 Procedure Rev.: 004 Report No.: 2-BOP-UT-14-040 Workscope: BOPNon-Outage Work Order No.: 396448 Page: 1 of 4 Code: Info Only Cat./Item: NIA/N/A Location: U2 TB 335' Drawing No.: 2HCC-2003-1

Description:

SW Leak at SS to CS FW-1 System ID: SW Component ID: 2HCC-2003-1 SW Leak Size/Length: 6" Thickness/Diameter: 0.280" Limitations: None Temp. Tool Mfg.: PTC Serial No.: 109537 Surface Temp.: 70 *F Couplant: ULTRAGEL II Batch No.: 12M020 Cal. Report No.: N/A Examination Surface: Inside El Outside W Surface Condition: Ground Flush Lo Location: TDC (leak at 24") loo TE P2 Wo Location: Centerline of Weld Tmin scan .069" o.24" o .3" Tmin grid .226" Tmax grid .577" Tavg grid .353" Comments:

• See Supplemental Report for 360* readings around pipe and Star pattern readings at leak location. Lowest scanned reading was 0.069" near leak. Equipment used: Panametrics 37DL Plus #51324510, Panametrics transducer D795 5 Mhz .2" #10101, CS Step #93-6900, SS Step10-3009 CAL IN/OUT acceptable. This flaw is considered Non-Planar Results: Accept E] Reject [. Info W Ref. CR-ANO-2-2014-2970 Percent Of Coverage Obtained > 90%> NIA Reviewed Previous Data: N/A Examiner Level ,I 5S atur S,/ Date Reviewer Signature Date Taylor, Michael W. / 1012112014 NIA A Examiner Level N/A Signate Date Site Review Signature Date NIA Panther, Ken -1 [ 4 1012212014 Other Level V)gnature Date ANII Review Signature Date Jackson, Rickey j A ( r- 10/2112014 N/A UT Thickness Examination

• Enterg Supplemental Report Report No.: 2-BOP-UT-14-040 Page: 2 of 4 Summary No.: FW-1 2HCC-2003-1 Examiner: Taylor, Michael W. I-Level: II Reviewer: N/A Date:

Examiner: NIA Level: N/A Site Review: Panther, Ken Date: 1012212014 Other: Jackson, Rickey ,', Level:

• A ANII Review: Date:

77 Comments: The leak was located at the toe of weld on the Sweep-o-let side of weld. UT readings taken In a Star pattern around leak location to establish a wear area. Each row Is incremented every 450 with each reading taken every .25" away from leak. This flaw Is considered Non-Planar.

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h Entergy Supplemental Report Report No.: 2-BOP-UT-14-040 Page: 3 of 4 Summary No.: FW-1 2HCC-2003-1 Examiner: Taylor, Michael W.IL Level: II Reviewer. NIA Date:

Examiner. N/A Level: NIA Site Review: Panther, Ken Date: 10122/2014 Other. Jackson, Rickey ,A/ Level: A ANII Review: N/A Date:

V Comments: UT readings taken 3600 around pipe at the plane of the leak for circuferential thicknesses. 01 reading was taken at TDC. Also scanned 100% circumferentlally around pipe looking for other low readings and none werefound. C2. r(J*_ ýs *,vj'f- 0d/

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"A"- taken on CS Sweep-O-Let, "B"- taken on weld, "C"- taken on SS Elbow Sketch or Photo: \\jdcnsetsp001\lDDEAL\lddeal Ver 8\lddealServertlddealANO\Documents\ANO BOP 2014\MIC\2HCC Gdd.jpg 11 A I it I r I Supplemental Report

• EnteWg Supplemental Report Report No.: 2-BOP-UT.14-o40 Page: 4 of 4 Summary No.: FW-1 2HCC-2003-1 Examiner Taylor, Michael W. Level: Ii Reviewer NIA Date:

• f Z Examiner N/A Level: NIA Site Review: Panther, Ken Date: 1012212014 Other Jackson, Rickey Level: ANII Review: NIA Date:

Comments: Pictures before and after grinding weld fiat. Picture on left shows weld still painted with stain appearing on SS elbow. Picture on the right is after grinding weld flat showing the leak to be at the toe of the weld on the Sweep-o-let side. 4.C A X iS i A) loofe TcSJ4  ? i, .

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